1. Field of the Invention
The invention relates generally to digital communications switching systems (sometimes referred to hereinafter as networks) that are circuit switch based, and to methods and apparatus for managing bandwidth allocation in such systems. More particularly, the invention relates to methods and apparatus that can be used to define, activate and manage virtual connections between network station devices, such as host computing resources, PCs, etc. These virtual connections are defined once, then they can be recalled and activated (i.e., be "switched on") as network resources are actually needed and become available. The resulting communication paths through the switching network, the "switched virtual connections" (SVCs), can be dynamically reconfigured depending on traffic conditions including data volume, channel availability, etc., thereby facilitating effective bandwidth management and other features.
2. Description of the Related Art
Communication systems are known which have the ability to integrate voice, terminal data and control communications throughout the system network. One such system is described in U.S. Pat. No. 4,612,634 issued Sept. 16, 1986 to John Bellamy, entitled "Integrated Digital Network". The U.S. Pat. No. 4,612,634 patent is assigned to the same assignee as the present invention and is referred to hereinafter as the "IDN". U.S. Pat. No. 4,612,634 is hereby incorporated by reference.
The IDN is a digital circuit switch that may be characterized in that it has the ability to integrate voice and data using common switching, control and distribution equipment.
More particularly the IDN taught in the referenced application includes a matrix switch and a plurality of user ports for exchanging voice, data and control digital signals between the matrix switch and user equipment. Digital switching and multiplexing techniques are used in the IDN system to provide simultaneous voice and data service at peripheral user ports into the system. Voice is PCM encoded onto a 64 kbps "bearer" channel at the station instrument. Each data stream uses an appropriate scheme to encode its output onto the same type of bearer channel as a PCM voice stream. Out-of-band signalling channels of various bit rates are used from the stations throughout the system.
The IDN includes a transmission system of bearer channels and a parallel control system of signalling channels. It uses a hierarchal channelization scheme which multiplexes all of the bearer and signalling channels into multiple 64 kbps subchannels which are carried over higher speed links to terminate on matrix ports at the matrix switch. The matrix switch interconnects the bearer channels of the transmission system and provides matrix signal ports to present signalling channels of the control system to the switch controller. In the preferred embodiment the IDN channels are combined by concentration units such that all interconnection with the central equipment is via 2.048 Mbps links. In addition, there are subsequent intermediate links between the concentrators and station devices which carry traffic at 256 kbps and 80 kpbs. A 2.048 Mbps link is hereinafter referred to as a GL-5 link, a 256 kbps link is hereinafter referred to as a GL-2 link and an 80 kbps is hereinafter referred to as a GL-0 link.
The user ports of the IDN provide access to station bearer and signalling channels. The transmission system includes, among other components, a plurality of station multiplex/demultiplex circuits (referred to hereinafter as "SMXs") servicing a cluster of user ports, for concentrating the digital signal samples from each port (which include both bearer and signalling channels) into channel signals for exchange with the matrix switch.
All bearer information carried by the IDN, e.g., voice, data and signal information, are switched through the matrix for transmission through the system. This allows for flexibility in configuring IDN information paths. Also, multiple levels of multiplexing are used to combine station port signals into higher order multiplex signals for transmission to the IDN matrix. This occurs remotely from the central matrix and is flexible, allowing for selected installation of any number of station ports where needed.
The remote multiplexing for the IDN is performed by Channel Multiplexers ("CMXs") which form an integral part of the IDN system as depicted in FIG. 1 of the incorporated patent. The figure shows CMXs being utilized as part of line and trunk interface (units 117 and 140 respectively), and further shows the CMXs in close physical proximity to and tightly physically coupled (via a shared backplane) to the Central Equipment Module (CEM).
Another circuit switch based communication system, which improves upon the IDN, is described in copending U.S. patent application, Ser. No. 07/372,885, filed June 28, 1989 entitled "Integrated Office Controller (IOC)", also assigned to the same assignee as the present invention.
The IOC, like the IDN, is a digital PCM information handling system for voice, and simultaneous handling of data signal communication between stations serviced by IOC station multiplexers.
The IOC network includes, in combination, a plurality of station devices, capable of transmitting and receiving multiplexed bearer and signal channel information; user port interface means for carrying said multiplexed bearer and signal channel information between a station device and a station multiplex/demultiplex device (SMX); a plurality of station multiplex/demultiplex devices (SMXs) each associated with and coupled to a predefined cluster of said station devices, via said user port interface means, for concentrating the multiplexed bearer and signal channel information, transmitted from said user port interface means toward said switch matrix, into channel signals, and for demultiplexing channel signals being transmitted toward the cluster of station devices coupled to a given SMX into multiplexed bearer and signal channel information for distribution to said station devices; transmission system means, capable of interfacing SMXs and trunk cards to a CEM, where SMX/CEM interfacing is performed by a Line Interface Module (LIM), and trunk/CEM interfacing is performed by a Trunk Interface Module (TIM); call processor, system clock means and matrix switch means, located in the CEM device, for switching said channel signals; and host processing means, coupled to the CEM, for providing support for programmable applications that include voice and data integration within the IOC network.
Reduced wiring and equipment cost, configuration flexibility and expansion possibilities are realized in the IOC (when compared to IDN) via the provision for modular LIMs and TIMs in the IOC system. Further cost reduction in LIM and TIM equipment (and transmission equipment generally) are realized by concentrating switch intelligence (call processing functions, feature cards, etc.) at the CEM level.
The IOC includes additional processing resources (when compared to the IDN) which provide simplified device access, station installation, call handling and PC integration, along with improved voice mail and electronic office capabilities.
Both the IDN and IOC as described in the incorporated references exemplify state of the art circuit switches that require definition and activation of duplex communication paths each time a given station device on the network wants to establish a connection to another station device on the network. Additionally, prior art integrated digital circuit switch networks of the type described in the incorporated references, require full period connections (FPCs) for all data paths (voice and data) through the network, where an FPC is defined as a connection that is active from the beginning to the end of a call even if there is no useful information being carried in the channel during some periods of the call.
A great deal of network overhead, i.e., network resource (controller, memory, bandwidth, etc.) utilization, is expended by repeatedly defining and activating the aforementioned paths. This overhead expense is presently necessary since no protocol exists in systems typified by the references for providing quick access between station devices through the matrix. Network resources are further wasted by utilizing full duplex connections and FPC protocols in situations not requiring these features. For example, a simplex, non-FPC path may be all that is required to allow a first computer coupled to the network to transmit a block of data to a second computer.
In addition to the aforementioned shortcomings pertaining to network overhead, known circuit switch based communications systems of the types described in the incorporated references do not have the broadcast capability typically found in packet switch or local area network (LAN) architectures. Such capability allows one device on the network to transmit data to two or more (or all) of the station devices attached to the network at the same time.
Well known LANs and packet switches, such as the LAN specified in the IEEE 802.3 specification and the packet switch described in the CCITT X.25 recommendations, provide both broadcast and quick switch access capabilities (i.e., eliminate the need for repeated call definition and establishment, etc.); however, the known systems with these capabilities are not circuit switches and are not capable of integrating voice and data using common equipment like the IDN and IOC.
Accordingly, it would be desirable to implement the aforementioned LAN and packet switch features (i.e. broadcast and quick access between devices) in a digital circuit switch environment (like the IOC) where common switch, control and distribution equipment are used for voice and data. Furthermore, it would be desirable to be able to implement these features using the existing switching, control and distribution hardware found in a circuit switch without having to, for example, expend data buffering overhead and centralized packet switching computer hardware to perform these functions.
Further yet, it would be desirable to be able to perform dynamic resource allocation and traffic analysis in the aforementioned circuit switch based systems so that maximum utilization of available bandwidth can be achieved while at the same time reducing network overhead.
Still further desirable circuit switch features include (a) providing the LAN and packet switch type broadcast feature without compromising the security inherent in circuit switch type communications and (b) controlling the fairness of access to data communication channels by all stations on the network, while at the same time providing quick access between station devices connected to the network.